1. Field of the Invention
The present invention relates to a power source system, a control apparatus of the power source system, and a control method of the power source system. More particularly, the present invention relates to a power source system, a control apparatus of the power source system, and a control method of the power source system, equipped with a fuel cell.
2. Description of the Related Art
In recent years, as an environmental problem and an energy problem have been getting popular, research and development which aim at putting a fuel cell, that have little influences on the environment (environmentally friendly), to practical use and at spreading the fuel cell have been vigorously performed. As a field to which a power source system using such fuel cell is applied, for example, a motor vehicle field can be cited. In the motor vehicle field, it has been required to put in practical use an electric vehicle using an electric motor as a drive unit in place of a gasoline engine and a diesel engine, and research and development for applying the power source system using the fuel cell as the power source unit to such electric vehicle have been vigorously performed. Consequently, the fuel cell is gradually being put in practical use and commercialized.
On the other hand, there have been demands to enhance the properties and extend period of operation time concerning portable type electronic equipment, which have been conventionally driven by a secondary battery, such as a personal digital assistant, a cellular phone, a digital still camera, a digital video camera, a portable television, a note-book size personal computer and the like. For such demands, research and development to miniaturize the power source system using such fuel cell as a power source unit that replaces the secondary battery have also been vigorously performed.
There is a fuel reforming type fuel cell as a fuel cell used for such a power source system. The fuel reforming type fuel cell is equipped with a chemical reaction unit such as a reformer for generating hydrogen by reforming a fuel for power generation containing a hydrocarbon compound through a chemical reaction of a catalytic reaction. In order to enhance the reaction in the chemical reaction unit efficiently, it is necessary to maintain the chemical reaction unit at a suitable predetermined temperature. As the method to maintain the chemical reaction unit at the predetermined temperature, for example, a configuration which supplies a required heat quantity using heat generation by a combustion component in the offgas ejected from a generator unit of a fuel cell and a fuel for combustion within catalyst combustor is known besides the heating by an electric heater.
However, when the output power of the generator unit of a fuel cell has changed or the temperature of the generator unit has changed according to the change in power requirement due to change in load, for example, the quantity of the combustion components in an offgas ejected from the generator unit changes, and leads to change in heat quantity by combustion heat due to the change of the quantity of the combustion components in the offgas.
Such change of the heat quantity is compensated by, for example, the combustion heat of the fuel for combustion, however, the catalyst combustor has a large time constant and a slow response to the injection of a fuel. Consequently, the compensation method has a problem in that it is difficult to stably control the temperature of the chemical reaction unit against a load change. Moreover, because it is difficult to control the temperature of the chemical reaction unit stably, the method also has another problem of a wasteful use of the fuel for burning.